A shock tube study of the reaction of methyl radicals with hydroxyl radicals

The reaction of CH₃ with OH has been studied near 1200 K and 1 atmosphere pressure in shock tube experiments in which UV absorption was used to monitor [OH]. A rate coefficient of (1.1 ± 0.3) × 10¹³ cm³/mol-s was measured for removal of OH by CH₃. This measured value is compared with previous experimental data and calculations. Several possible reaction channels are discussed, and although products were not monitored, it seems probable, on the basis of other work and theoretical estimates, that the primary mechanism (?75%) for the removal of OH by CH₃ at these conditions is their combination to form CH₃OH. Rate coefficients of (5.3 ± 0.8) × 10¹² and (9.0 ± 1.4) × 10¹² cm³/mol-s were measured for the reactions of OH with acetone and ethane, respectively, at the same temperature and pressure.     

Optical probing of thin liquid crystal layers using the prism-coupling technique

Prism-coupling work in polymer aligned liquid crystal layers is presented with special emphasis being placed on the ferroelectric chiral smectic C phase, of interest to electro-optic device fabrication. Experimental results as a function of temperature, wavelength and DC applied voltage are presented, together with a study of sp mixing which may have potential device applications as well as being an elegant technique with which to establish the optical dielectric tensor configuration in thin, aligned liquid crystal layers.     

The liquid-crystalline behaviour of amphiphilic ethane-1,2-diol derivatives incorporating a six membered ring in their principal structure

Novel 3-phenyloxy substituted propane-1,2-diol derivatives, 4-(4-n-hexyloxyphenyl)-butane-1,2-diol and 4-(trans-4-n-pyropylcyclohexyl)-butane-1,2-diol have been synthesized and their thermal behaviour has been studied. These compounds exhibit thermotropic and, after addition of water, also lyotropic liquid-crystalline behaviour. The clearing temperatures of the smectic mesophases were found to be strongly dependent on the alkyl chain length and on the structural units that link the aromatic ring to the alkyl chain and to the diol unit. The behaviour of the aromatic compounds is compared with that of the cyclohexane derivative. Thereby it has been realized that the mesophase stability of the amphiphilic diols incorporating a rigid unit is largely determined by both, the molecular geometry (molecular shape and intramolecular flexibility) and the amphiphilic structural pattern.     

The Cern (g-2) measurements

Measurements of the anomalous magnetic moment of the muon are reviewed. The emphasis is put on the first one of a series of three CERN experiments which led to an experimental value ofa=1165922.9 (8.5)·10⁻⁹ (±7.2ppm), and which compares well with the present theoretical resulta=1165919.2 (1.8)·10⁻⁹ (±1.5ppm).     

Magnetic resonance findings in sarcoidosis of the thorax.

Fifteen patients with sarcoidosis underwent thoracic MRI examinations. The T2 signal intensity of lymphadenopathy varied, with no characteristic pattern noted. Three of four patients with bright lymph nodes on T2 images had stage I sarcoidosis, but low intensity nodes were also seen in stage I patients. Coronal images were complementary to axial images and better depicted subcarinal adenopathy. MRI does not distinguish the lymphadenopathy of sarcoidosis from other entities, but is useful for defining the anatomic extent of disease and differentiating pulmonary artery enlargement from adenopathy.     

On the retrograde condensation of one or two liquids

This contribution discusses the phenomena of retrograde condensation of one or two liquids. It w1 be shown that both phenomena can be well understood. Also the relation of retrograde condensation of one liquid phase with the condensation behavior of natural gas will be discussed. Similarly that of two liquid phases with multiple phase behavior occurring in low temperature reservoir fluids will be pointed out.     

A Tabu Search Approach for Delivering Pet Food and Flour in Switzerland

In this paper, we consider a real-life vehicle routeing problem that occurs in a major Swiss company producing pet food and flour. In contrast with usual hypothetical problems, a large variety of restrictions has to be considered. The main constraints are relative to the accessibility and the time windows at customers, the carrying capacities of vehicles, the total duration of routes and the drivers' breaks. To find good solutions to this problem, we propose two heuristic methods: a fast straightforward insertion procedure and a method based on tabu search techniques. Next, the produced solutions are compared with the routes actually covered by the company. Our outcomes indicate that the total distance travelled can be reduced significantly when such methods are used.